RE: [RFC PATCH 01/56] Documentation/admin-guide: Add documentation

Kaplan, David
2025-10-20T13:53:15Z

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Borislav Petkov <bp@alien8.de>
> Sent: Saturday, October 18, 2025 8:39 AM
> To: Kaplan, David <David.Kaplan@amd.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>; Peter Zijlstra <peterz@infradead.org>;
> Josh Poimboeuf <jpoimboe@kernel.org>; Pawan Gupta
> <pawan.kumar.gupta@linux.intel.com>; Ingo Molnar <mingo@redhat.com>; Dave
> Hansen <dave.hansen@linux.intel.com>; x86@kernel.org; H . Peter Anvin
> <hpa@zytor.com>; Alexander Graf <graf@amazon.com>; Boris Ostrovsky
> <boris.ostrovsky@oracle.com>; linux-kernel@vger.kernel.org
> Subject: Re: [RFC PATCH 01/56] Documentation/admin-guide: Add documentation
>
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> On Mon, Oct 13, 2025 at 09:33:49AM -0500, David Kaplan wrote:
> > +Move Policy To Userspace
> > +^^^^^^^^^^^^^^^^^^^^^^^^
> > +
> > +Mitigation choices are related to the security policy and posture of the system.
> > +Most mitigations are only necessary on shared, multi-user systems if untrusted
> > +code may be run on the system, such as through untrusted userspace or
> untrusted
> > +virtual machines. The kernel may not know how the system will be used on
> boot,
> ^^^^^^^^^^
>
> "after it has been booted" I'd say.

Ack

>
> > +and therefore must adopt a strong security posture for safety.
> > +
> > +With dynamic mitigations, userspace can re-select mitigations once the needs of
> > +the system can be determined and more policy information is available.
> > +
> > +Mitigation Testing
> > +^^^^^^^^^^^^^^^^^^
> > +
> > +Dynamic mitigation support makes it easy to toggle individual mitigations or
> > +choose between different mitigation options without the expense of a reboot or
> > +kexec. This may be useful when evaluating the performance of various
> > +mitigation options. It can also be useful for performing bug fixes without a
>
> "for fixing bugs in the mitigations themselves" - simpler
>
> > +reboot, in case a particular mitigation is undesired or buggy.
>

Ack. Although to be clear, all it can do is select a different mitigation. For instance, if there was a bug in safe-RET, it can't fix that bug. But it could allow selecting a different SRSO mitigation.

Thanks
--David Kaplan